Amplifier arrangements employ different linearization methods enabling the occurrence of interfering signals, such as distortions, noise and non-linear distortion, to be reduced in an output signal of an amplifier.
U.S. Pat. No. 5,420,536, for example, discloses a non-linear amplifier linearization method based on a feedback circuit in an amplifier.
In FI 9602814, linearization is carried out by predistorting a signal to be coupled to an output stage. The linearization is based on the fact that a device implementing the predistortion and the output stage have inverse operating characteristics compared with each other.
The solution disclosed in U.S. Pat. No. 5,136,257 comprises measuring the output power of an amplifier, which is compared to a predicted value. The solution employs feedback, and information obtained from the feedback is used for adjusting the bias of a multi-stage amplifier. The solution disclosed is relatively complex to implement.
The linearization methods based on feedback are not particularly suitable for use in effective amplifier stages. The linearization methods are not optically suitable for use in amplifiers amplifying high frequency signals either. Furthermore, the known linearization methods are relatively complex to implement.